Members of the Heracleum genus are hardy perennials that reach great heights of between 2.5 and 5.5 metres.
They carry small white or pink flowers in umbels atop thick stems. They are ideal plants to grow in a wild flower garden or close to water.
Some common names for Heracleum include Cow Parsnip, Giant Hogweed, Cartwheel flower and Masterwort.
Heracleum sphondylium - Hog Weed by Mick E. Talbot.
Common Names: Hogweed, Giant Hogweed, Cow Parsnip, American Cow Parsley, Cartwheel Flower, Giant Masterwort.
Life Cycle: Hardy perennial.
Height: 110 to 144 inches (280 to 365 cm).
Native: Central Asia.
Growing Region: Zones 3 to 9.
Flowers: Middle of summer.
Flower Details: White, pink. Umbels.
Sowing: 1/4 inch (6 mm). Germination time: one to three months.
Seed: Method 1: Seeds should first be sown into peat pots in the autumn. Next sink the pots into the ground in an area that offers shade, preferably close to a wall that faces north. Provide a glass/plastic covering. Keep an eye on the pots to ensure that the soil remains moist. Bring the pots indoor in spring. Transplant to the final location in autumn.
Seed: Method 2: In the spring, sow seeds in a peat pot, wrap in a plastic bag, then stratify by refrigeration for three weeks. Next bury the pots as described above. Once seedlings emerge remove the covering. Transplant them as above.
Requirements and care: Full sunlight or light shade. Rich soil, moist soil. Deadhead. Propagate: Self seeds readily; dividing in the spring or the autumn.
Miscellaneous: Invasive species in many areas especially parts of North America and Europe. Wear gloves as touching the Giant Hogweed plant may lead to Phytophotodermatiti resulting in skin rashes. The seeds of Persian Hogweed are used in powder form with beans in order to reduce flatulence.
When growing Cow Parsnips outdoors they should be prepared in the spring or autumn. Spring sowing of Cow Parsnips is discussed here. The seeds should be sown in peat pots at a depth of 6 mm then the pots put in a black plastic bag, and placed in the the fridge for three weeks. The pots should then be transferred and sank into a shady part of the garden and covered with glass. Let the seedlings that appear grow until the autumn, then transplant the young cow parsnips into a sunny or partially part of the garden that has a rich and moist soil. As they are large plants, Heracleum should be spaced at about 1 to 1.25 m apart.
It is important to keep on top of Cow parsnips and other Heracleum Plants as they are invasive plants that will take over the garden given half a chance.
It is necessary to remove the flowering stems once they appear; wear gloves when doing this as the leaves of the Heracleum plant are toxic and may cause a skin rash. If you require more plants then they can be had by division.
I hope that you enjoyed this guide on how to grow Heracleum plants. Updated September 2020.